Patio door locking mechanisms are typically centrally located at the end of a door and reciprocate a bolt or bolts at both the top and bottom of the door between locked and unlocked positions. These mechanisms have been constructed with linkage arrangements which reciprocate both bolts together. However, the linkages which have been used have directed forces at relatively large angles to the desired reciprocal direction of motion and thus have created frictional forces in slider joints which inhibit the movement of the mechanism. The friction also tends to increase wear on the linkage components, thereby reducing the life span of the mechanism.
Prior mechanisms have had the components constructed and arranged whereby substantial space is required and which is difficult to provide in a door such as a sliding patio door wherein the glass panels are surrounded by a narrow frame.
An example of a linkage used heretofore is shown in U.S. Pat. No. 998,642, issued July 25, 1911, showing a four bar linkage of the slider crank type applied to non-aligned bolts. The links apply as much undesirable lateral force to the actuating rods for the bolts as they do axial force, thereby causing the rods to bind and wear against the guide bracket plates. The sliding of the rods in the guide bracket plates not only creates friction which inhibits vertical motion of the rods, that friction further causes wear between the rods and guide plates, thereby shortening the life span of the working parts.
The present invention is directed to overcoming one or more of the problems as set forth above.